Showing papers in "Transactions of The Royal Society of Tropical Medicine and Hygiene in 1977"

An improved parasitological technique for the diagnosis of African trypanosomiasis.

Abstract: Light microscopic examination of the buffy coat zone of a microhaematocrit capillary tube expressed on to a slide was found to be consistently more reliable than other standard techniques in detecting trypanosomes in the circulation of cattle. This method alaos allowed identification of different trypanosome species. Optimal results were obtained using darkground illumination.

The identification by isoenzyme patterns of two distinct strain-groups of Trypanosoma cruzi, circulating independently in a rural area of Brazil

Abstract: Culture forms of 17 Trypanosoma cruzi stocks, primarily isolated from a rural area of endemic Chagas disease at Sao Felipe, Bahia, Brazil, were compared by the electrophoretic patterns of six enzymes: aspartate aminotransferase, alanine aminotransferase, glucose-6-phosphate dehydrogenase, malate dehydrogenase (decarb-oxylating) (NADP+), glucosephosphate isomerase and phosphoglucomutase. Two markedly distinct combinations of isoenzyme patterns were seen, justifying the arrangement of the 17 stocks into two strain-groups, each of which was enzymically homogeneous. One combination was characteristic of the 11 domestic stocks of T. cruzi derived from both human infections and domiciliated animals; the second was characteristic of the six sylvatic stocks derived from opossums and a sylvatic triatomine species. The enzyme patterns were independent of the original host and the type of culture medium used. Distinction of the two strain-groups accords with epidemiological evidence that the domestic and sylvatic transmission cycles in Sao Felipe do not overlap. It is suggested that the diverse enzyme characters of the two strain-groups circulating in Sao Felipe reflect diverse origins; the domestic form of T. cruzi probably invaded the area from the south of Brazil with the domestic triatomine vector, Panstrongylus megistus.

Infection and its effect on the growth of young children: a comparison of The Gambia and Uganda.

Abstract: Longitudinal studies of 152 children from Keneba, The Gambia, and 45 from Namulonge, Uganda, investigating the relationship between growth and different types of infection in the two areas are reported and their relevance to the patterns of malnutrition seen in Africa are discussed. The relative ineffectiveness of curative medicine in the real health problems of rural Africa and the need for prevention are stressed.

Blood pressure distribution in a rural Ghanaian population

Abstract: Hypertension and related complications appear, from clinical impression, to be increasing problems in urban Ghanaians. In early 1973 we conducted a blood pressure survey in 20 rural Ghanaian villages to determine the prevalence of hypertension, in comparison with studies done in Accra residents and black Americans. Rural Ghanaians had mean systolic and diastolic blood pressures which were lower at all ages than the urban groups. 2·5% of the subjects aged 16 to 54 years had diastolic blood pressures of 95 or higher mm Hg. These findings are discussed in view of the proposed hypertension control programme in Accra. We conclude that hypertension is not a significant health problem in rural Ghanaians and that large-scale hypertension case-finding and intervention programmes should be confined to urban populations.

Dengue virus infections in Nigeria: a survey for antibodies in monkeys and humans.

Abstract: A retrospective serological survey for dengue immunity was conducted in Nigeria to determine the prevalence of infection in man and non-human primates. Preliminary haemagglutination-inhibition (HI) tests revealed that 63% of persons tested had HI antibodies against one or more of the following flaviviruses: dengue type 1, yellow fever, West Nile and Wesselsbron. Parallel HI and neutralization (N) tests on 179 human sera showed that six of 20 sera (30%) negative for flavivirus HI antibody contained dengue N antibody. This finding emphasized the advantage of the N test over HI in screening for dengue virus immunity. Neutralization tests performed on 1,816 human sera from different geographical locations in Nigeria showed that 45% of Nigerians were immune to dengue type 2 virus. The percentage of immunity in adults aged 20 years and older (51%) was significantly higher than in children (37%) (P less than 0-01). In all four ecological zones sampled, the highest percentage of dengue N antibody was observed in the derived Savannah zone (63%) followed by the rain forest zone (42%). The Southern Guinea savannah and plateau zones had lower percentages of dengue-immune persons. There was a higher prevalence of antibodies in urban (48%) than in rural communities (37%). Tests on dengue-immune sera showed that 35% of such sera contained N antibodies to dengue only or to dengue and one other virus. Therefore, dengue immunity cannot be explained by heterologous cross reactions within the flavivirus group. In addition, evidence of dengue infection was found in monkeys and galagos. 48% of monkeys and 25% of galagos contained dengue N antibody. The presence of specific dengue N antibodies in a few sera suggests that the occurrence of a forest cycle of dengue is possible in Nigeria.

Malnutrition and gastroenteritis in The Gambia.

Abstract: There is a strong association between failure to thrive and diarrhoeal disease in young Gambian children. The high prevalence of diarrhoeal disease seen is not due to frequent attacks of “acute infantile diarrhoea” of viral origin. The picture of protracted diarrhoea is almost certainly due to colonization of the upper bowel and the high prevalence demonstrated to be at least partly due to the environment to which the children are exposed, particularly in terms of food and water hygiene. Until this cycle of upper bowel colonization and protracted diarrhoea is broken, a diet-based nutrition programme cannot be expected to function effectively.

The Duffy blood group and malaria prevalence in Gambian West Africans.

Abstract: Erythrocytes from 1,168 donors, comprising almost the entire populations of two rural Gambian villages, have been tested for Duffy blood group antigens using antisera to both Fya and Fyb. All tests were negative. Blood film examination of the same samples showed complete absence of Plasmodium vivax parasitaemia, but infections with P. falciparum,P. malariae and P. ovale were observed. The findings are consistent with the view that the Duffy-negative phenotype, FyFy, constitutes the basis of innate resistance towards infection with P. vivax but not towards infection with the other plasmodial species.

Host antigens and parasite antigens of murine Schistosoma mansoni.

Abstract: An indirect fluorescent antibody technique was used to detect mouse host antigens and parasite antigens on the surface of Schistosoma mansoni. A rabbit anti-mouse rbc antiserum was used to detect host antigens, and serum from mice immune to S. mansoni was used to detect parasite antigens. Schistosomula prepared after penetration of isolated mouse skin did not possess host antigens but bound antibody from immune serum (immune antibody); schistosomula recovered from the lungs of mice five days after infection possessed host antigens and failed to bind immune antibody. In contrast, schistosomula recovered from the skin of normal or immune mice three and 20 hours after cercarial penetration, adult worms, and cryostat sections of adult worms, were positive for host antigens but also bound immune antibody. Strong binding of immune antibody only occurred with the cryostat sections. Anti-schistosome antibody can therefore bind to schistosomes in the presence of host antigen. The lung forms of schistosomula, however, may have different surface properties as there is no evidence that immune antibody binds to these forms.

Strain differences in Echinococcus granulosus, with special reference to the status of equine hydatidosis in the United Kingdom

Abstract: The genetics of speciation in the genus Echinococcus are briefly discussed. As the organism is a hermaphrodite and multiplies asexually in the larval stage, the genetic mechanism for the ready production of new strains is inherent in the life-cycle. Some biological, biochemical and nutritional differences between the horse and sheep strains are examined. The sheep strain may be grown to sexual maturity, in vitro, in a diphasic system; the horse strain fails to grow in such a system. Differences have also been demonstrated between the soluble proteins of the two strains. The sheep strain is infective to man but, probably, non-infective to horses. The horse strain (which is now the major strain in the U.K and Ireland) appears to be poorly infective to sheep and may prove to be non-infective to man. The importance of determining the basic characteristics of other strains of E. granulosus are also stressed.

Toxocaral larva migrans: the use of larval secretory antigens in haemagglutination and soluble antigen fluorescent antibody tests

Abstract: Toxocara larval excretions and secretions collected from in vitro culture were used as antigen in passive haemagglutination and soluble antigen fluorescent antibody tests for the diagnosis of visceral larva migrans in experimental animals and man. Antibody to toxocaral secretions was detected in rabbits within 13 days of light Toxocara infection (ten larvae per kg) and within four days of heavy infection (10(4) larvae). Antibody was not detected following infection with 10(4) Ascaris suum larvae. In human sera, antibody was detected at low titre in 1% of 100 healthy adults and in 2% of 50 children. High titres were observed in one third of 170 patients with suspected visceral larva migrans and in 23 of 27 such patients presenting with an eosinophilia greater than 20%. In 25 patients with ocular lesions of an undiagnosed nature, four showed significant levels of anti-Toxocara antibody.

The natural decline of Wuchereria bancrofti infection in a vector control situation in the Solomon Islands

Abstract: In a situation where filariasis and malaria are transmitted by the same vector, as seen here in the Solomon Islands, the Malaria Eradication Programme aimed at controlling the vector, was found to have an effect on both diseases. In an area of Choiseul island first surveyed by the author in 1970, three follow-up surveys were conducted—in 1974, 1975 and 1976. These showed a progressive decrease in persons infected. When the densities, especially the median microfilarial counts, were expressed as percentage values of the pre-spray survey, there was found to be a proportional decrease over eight years. It is possible that the Anopheline vector needs to be reduced less for the cessation of transmission of filariasis than for malaria. A theoretical ratio was calculated and supporting field evidence presented.

Plasmodium falciparum gametocytes: The effect of chloroquine on their development.

Abstract: Asexual erythrocytic parasites of Plasmodium falciparum are killed by chloroquine, whilst mature gametocytes are not. The gametocytes of P. falciparum take 10 days to develop to maturity and their sensitivity to chloroquine during this time was studied in vitro to investigate when the switch from susceptibility to insusceptibility occurred and to compare the responses of asexual and immature sexual parasites to the drug. 45 to 50% of asexual parasites and immature gametocytes less than one day old survived in 0.1n. mols of chloroquine per ml but 0.3n. mols of drug per ml was lethal to both. Chloroquine at 1.0n mols per ml was lethal to developing gametocytes during their first six days of growth probably due, at least in part, to the drug disorganizing the parasite's digestion of host erythrocyte haemoglobin. The drug clumped the pigment of developing gametocytes. Only immature gametocytes in the final stage of development (stage 4) survive in high chloroquine concentrations.

A comparison of isotopic and enzyme-immunoassays for tropical parasitic diseases

Abstract: A comparison is made of enzyme-immunoassay and radio-immunoassay for the detection of antibody in Chagas's disease, sleeping sickness, malaria, schistosomiasis and invasive amoebiasis. Both assays were sensitive and reproducible and gave comparable results.

Trypanosoma brucei: detection of low parasitaemias in mice by a miniature anion-exchanger/centrifugation technique

Abstract: A method is described for the detection of trypanosomaemia in mice using the samples of about 55 microliter of blood which can be readily obtained from mice by puncture of the retro-orbital plexus with heparinized glass microhaematocrit tubes. The samples, mixed with an appropriate diluent, are passed through small (2 ml) anion-exchanger columns by means of peristatic pumps and the eluates collected in tubes which can be centrifuged so as to concentrate any organisms in the terminal part of the tube, of calibre about 200 micrometer, for microscopical examination. Evidence is presented to show that the method is more sensitive than other methods in use. It is also quick, requiring only some five minutes per mouse examined.

Leishmaniasis in Tuscany (Italy): (I) An investigation on phlebotomine sandflies in Grosseto Province

Abstract: A survey of phlebotomines has been made in the area of the Province of Grosseto (Tuscany, Italy) where human cases of both visceral and cutaneous leishmaniasis have recently occurred. 12 collecting stations, placed around the leishmaniasis foci, were divided into three groups of localities, the Argentario Promontory, coastal plains territory and hilly inland territory. Sandflies were collected with lit and unlit oil traps, and by hand. A total of 11,032 specimens (57% males) were caught and identified. Of these, 86·6% were Phlebotomus perfiliewi, 10·8% P. perniciosus and 2·3% Sergentomyia minuta; only a few specimens were P. papatasi and P. mascittii. In the first group of localities, P. perniciosus was very abundant (87·8%) and S. minuta scarce (12·0%); in the second group, P. perfiliewi was the only species collected; in the third group, P. perfiliewi was very abundant (98·0%), S. minuta was very scarce (1·1%) and P. perniciosus even more so (0·7 %). P. perniciosus is thought to be the probable vector of visceral leishmaniasis in the area of Monte Argentario and P. perfiliewi is strongly suspected of playing a role in transmission of the cutaneous form in the third group of localities. The species responsible for transmitting visceral leishmaniasis in some of the foci in this area is yet to be found.

A comparison of the pathogenesis of protein-energy malnutrition in Uganda and The Gambia

Abstract: The pattern of growth, biochemical and endocrine development, dietary intake and disease patterns of rural children in Uganda and The Gambia have been monitored during the first three years of life in order to gain a more complete understanding of the reasons why in Uganda kwashiorkor predominates, whereas in The Gambia it is marasmus. Evidence is produced which supports the view that the hormonal balance, particularly cortisol and insulin status, can have a profound influence on which organs of the body are preferentially affected by malnutrition and hence on the type of protein-energy malnutrition which is likely to emerge. There were, however, also important differences in protein and energy intake between the two countries.

Schistosomiasis mansoni: blockage of cercarial skin penetration by chemical agents: I. naphthoquinones and derivatives

Abstract: Skin penetration by Schistosoma mansoni cercariae may be blocked by 1,4-and 1,2-naphthoquinones applied topically. Of 23 naphthoquinone derivatives synthesized, 15 afforded almost complete protection when applied in solution to the tails of mice 24 hours before exposure to cercariae. On the basis of present evidence the 5-carbon atom side chain present in naturally occurring lapachol seems to be important for activity, and this is in accord with the previous observation that effective protective agents are liposoluble. Topically applied cercarial penetration inhibitors are presently the only prophylactic agents available for use in the field.

Lymphocyte changes in acute malaria.

Abstract: Lymphocyte sub-populations were studied in children with acute malaria. Depletion of T cells was found associated with an increased proportion of null cells. K cell activity for chicken red cells was also increased and it is likely that some of the increased number of null cells were K cells. An increase in K cell activity in acute malaria could be part of a protective immune response.

Cardiac and pulmonary involvement in leptospirosis.

Abstract: The clinico-pathological features of cardiac and pulmonary involvement were studied in seven cases of fatal leptospirosis. Petechial haemorrhages occurred in the heart and pericardium in all cases with blood-stained pericardial effusions in five. Interstitial myocarditis was noted in five patients and probably caused the changing electrocardiographic abnormalities and clinical cardiovascular effects during the illness. Sub-pleural and intra-pulmonary haemorrhages occurred in all seven cases with pleural effusions in four. Pulmonary oedema was a striking feature during the early stages of the illness, while in patients surviving the first week of the disease infiltrative and proliferative lesions were common. The latter type of pulmonary changes occurred at a stage when acute renal failure was improving and were not related to the presence and severity of jaundice. The clinico-pathological profile of pulmonary involvement in leptospirosis appears to fall into an adult respiratory distress syndrome and, when present, carries a serious prognosis and would then be a prime factor in mortality. As clinical manifestations of pulmonary involvement appear late during the clinical illness and may be of abrupt onset, auscultatory and radiological surveillance becomes mandatory in severe leptospiral infections.

A yellow fever epizootic in Zika Forest, Uganda, during 1972: Part 1: Virus isolation and sentinel monkeys

Abstract: The results of the yellow fever immunity survey of Central and East Africa reported by SAWYER & WHITMAN in 1936 prompted scientists to undertake well-planned epidemiological studies on yellow fever in eastern Africa. A Yellow Fever Research Institute (the present East African Virus Research Institute) was established at Entebbe in 1936 for this purpose. One of the areas where much work has been carried out is a strip of typical tropical forest, the Zika Forest, 12 kilometres from the Institute. Routine surveillance work, particularly on the biting activity of the yellow fever vector mosquitoes, has been going on since 1946. It was during one of these studies in 1972 that the first yellow fever virus strain was isolated from Aedes africanus collected from the Zika and Sisa forests and one strain was isolated from Coquillettidia fuscopennata, also from the Zika Forest. Three sentinel rhesus monkeys, nomimmune to YF, which were kept in the Zika Forest during the time of the epizootic died of YF disease. The present observations indicate that YF is still present in Africa, and as such it still remains a potential menace to the human population. The epidemiological implications are discussed.

Louse-borne relapsing fever: I. A clinical and laboratory study of 363 cases in the Sudan

Abstract: Louse-borne relapsing fever seems to have become endemic in the southern Sudan. The epidemic history of the disease in the Sudan is reviewed. We have studied 363 Sudanese patients involved in an outbreak of louse-borne relapsing fever in Khartoum (Sudan) between January and June 1974. 318 of the 363 patients were new immigrants from the soughern Sudan to Khartoum. The clinical presentation varied. The common clinical fetures of the disease were: fever (94%), headache (85%), hepatosplenomegaly (74%), body and joint pains (66%), abdominal pain and tenderness (63%), jaundice (46%) and epistaxis (40%). Thrombocytopenia was common. Biochemical evidence of hepatocellular and renal damage was present in most patients. The mortality rate was 5-5% with treatment. Post-mortem examination was performed on six cases. The organs predominantly involved were the liver, spleen, brain and lungs. The common causes of death were severe hepatic damage, lobar pneumonia, subarachnoid haemorrhage and splenic rupture.

The epidemiology of infection with Entamoeba histolytica in the Gambia, West Africa.

Abstract: A country-wide stool survey of The Gambia showed the prevalence of Entamoeba histolytica cysts to range from 13.7% up-country in the dry season to 52.3% near the coast. A longitudinal survey showed a near 100% infection rate over one year and a sharp rise in prevalence as the rains commence with an equally sharp fall as the rains progress. Specific antibody levels are elevated and reasonably constant through the year. Carriers generally show no specific lymphocyte reactivity to amoebic antigen but consistently parasite-negative individuals tended to show elevated lymphocyte reactivity. Attempts to discover the presence of cysts in the environment of villages by cultivation of specimens of water, soil, food, flies and washing from clothes and hands generally failed though E. histolytica was recovered once from a well.

Recovery of infective Schistosoma mansoni schistosomula from liquid nitrogen: A step towards storage of a live schistosomiasis vaccine

Abstract: Successful recovery of infective schistosomula of Schistosoma mansoni following storage at −196 °C is reported. The technique involves a two-step cooling procedure—slow cooling (0.65 °C min−1) to an intermediate temperature of −28 °C, followed by rapid cooling into liquid nitrogen (10,000 °C min−1). Rewarming (10,000 °C min−1) and rapid dilution to remove the cryoprotectant (17.5% methanol) yielded motile organisms some of which developed to adult worms in mice after intramuscular injection. The percentage of schistosomula developing to adult worms was small (044%), but is a significant step towards storage of trematode larvae and of a live attenuated vaccine for schistosomiasis.

The treatment of severe falciparum malaria.

Abstract: In severe falciparum malaria there is a pathophysiological cascade beginning with changes in the parasitized red blood cells which induce intermediate effects, in turn contributing to dysfunction of several organs. A low serum albumin is a common but often unrecognized finding which may contribute to oedema especially in the lung and brain. The only irreversible complication in falciparum malaria is the acute respiratory distress syndrome, manifested by cyanosis and rapid breathing, basically distinct from acute pulmonary oedema caused by therapeutic overhydration. The pathophysiology of falciparum malaria may be complex but the treatment is simple. Drugs, other than antimalarials, are rarely needed. Guidelines for cholorquine or quinine dosage in severe disease are proposed; each drug is given at a dose of 5 to 10 mg/kg in 10 ml/kg of fluid as an intravenous infusion in four hours at a frequency of dosing every 12 to 24 hours. When the disease has been brought under control the treatment should be changed from the intravenous to the oral route.

Mycoses of the Sudan.

Abstract: Mycoses in the Sudan are still significant and, as well as mycetoma, there are a number of fungal diseases: paranasal aspergillus granuloma, which came into eminence in 1966; actinomycosis; subcutaneous phycomycosis; systemic phycomycosis; post-operative opportunistic infection of the eye with Trichosporon cutaneum and rhinosporidiosis. Mycetoma and paranasal aspergillus granuloma are discussed in detail.

A yellow fever epizootic in Zika Forest, Uganda, during 1972: Part 2: Monkey serology

Abstract: During the 1972 yellow fever epizootic in Zika Forest, Uganda, sera from 21 monkeys shot in a number of forests around the Entebbe area were tested for the presence of a number of arbovirus antibodies. All sera were tested for antibodies against Chikungunya (CHIK), O'nyong-nyong (ONN), Zika, yellow fever (YF) West Nile (WN) and Wesselsbron (WESS) by the haemagglutination-inhibition (HI) test. Because of the crossreaction within the flaviviruses (group B arboviruses) mouse protection test (PT) was also carried out on the sera against YF, WESS and Zika viruses. Serological studies carried out on monkey sera from different parts of Uganda, including the Entebbe area, during 1968 gave results which reflected a surprisingly low rate of YF immune monkeys (3%) throughout the country compared with the rate of over 40% immune monkeys obtained by Haddow et al. in 1951. 40% of the monkey sera collected during 1972 were immune to YF by the PT. Since no YF virus had been isolated between 1968 and 1972 the results indicate strongly that the monkeys in the Entebbe area were involved in the epizootic of 1972. No sick or dead monkeys were found in all the forests checked around Entebbe area during the epizootic. This indicates that the animal-to-animal cycle of the equatorial African forests involved the mild endemic infection characteristic of a virus in its natural habitat and infecting its natural host.

Immunofluorescent reactions with microfilariae: 1. Diagnostic evaluation

Abstract: Microfilariae have been evaluated as antigen for the indirect immunofluorescent test in the diagnosis of filariasis. Sonicated, unlike whole, microfilariae present no problems in handling on a slide. The cytoplasmic antigen that is exposed by sonication, unlike the sheath or cuticular antigen, reacts with filariasis sera irrespective of whether or not there is a detectable microfilaraemia. The cytoplasmic antigen of microfilariae of various species was marginally superior to Dirofilaria adult worm as antigen for diagnostic immunofluorescence in respect of both sensitivity and specificity. The microfilariae extruded from the uterus of an adult D. immitis were a useful source. But the best results were obtained with the sonicated microfilariae of Brugia pahangi , with which it was possible to utilize both cytoplasmic and sheath antigens simultaneously, giving a positivity rate of 95% for filariasis infections as a group. This test is thought to be the best available at present for the sero-diagnosis of filariasis, in spite of some lack of specificity. For individual filarial infections a homologous microfilarial antigen is probably the ideal.

The immunological diagnosis of human hydatid disease

Abstract: There is evidence that the yearly incidence rate of hydatid disease may be increasing in endemic areas and in regions of the world hitherto free of the infection. The availability of an accurate method of detection in both man and other animals would facilitate understanding of the global epidemiology. The diagnostic procedures in use in human hydatidosis have often given inconclusive results in animal infections. The following tests are discussed and their usefulness appraised: intradermal, complement fixation, haemagglutination, latex agglutination, indirect fluorescent antibody, immunoelectrophoresis, counter immunoelectrophoresis, enzyme linked immunosorbent assay, radio-immuno assay and lymphocyte transformation.